1. Examining 802.11ba Usage Models for Mainstream Devices
Month Year
doc.: IEEE yy/xxxxr0
Sept 2017
Examining ba Usage Models for Mainstream Devices
Date:
Name
Affiliations
Address
Phone
Guoqing li
Apple
Oren Shani
Chris Hartman
Jarkko Kneckt
Minyoung Park
Samsung
Bin Tian
Qualcomm
Alfred Asterjadhi
Hongyuan Zhang
Marvell
Liwen Chu
Po-Kai Huang
Intel
Shahrnaz Azizi
Robert Stacey
Ross Yu
Huawei
Vinko Erceg
Broadcom
Bo Sun
ZTE
Apple
John Doe, Some Company

2. Sept 2017 Apple Name Affiliations Address Phone email James Yee
MediaTek
Chaochun Wang
James Wang
Apple

3. Sept 2017
Introduction
Most of the use cases described in ba Usage model document [1] are targeting IoT market, and we think that current design in ba will benefit such IoT devices
However, we believe that, to make ba a truly successful standard, it needs to bring significant benefit for mainstream devices to adopt it as well
Note that ba is a new radio for main stream devices. Integrating such a new radio takes huge amount of effort on HW integration, SW integration, new co-existence management and connection management, intensive HW/SW testing etc.
Therefore, the benefits brought by ba have to be significant enough in order to be adopted by mainstream devices
This contribution examines the benefits and issues of using ba on main stream devices such as smart phones, and proposes new use cases that can be (almost) readily enabled by ba which can bring more significant benefits for mainstream devices
Apple

4. Month Year
doc.: IEEE yy/xxxxr0
Sept 2017
Introduction
802.11ba is targeting at saving Wi-Fi power consumption during the no-real-traffic period without sacrificing the delay performance when real traffic arrives
The power saving mainly comes from two factors:
Beacon reception during Idle period
Wi-Fi main radio may be put to deep sleep mode or turned off completely
Case 1: without 11ba
Beacon
Beacon
Main radio
Sleep
Sleep
Case 2: with11ba
Main radio
Sleep or off
11ba
802.11ba power
Slide 4
John Doe, Some Company

5. 802.11ba for Main Stream Devices
Sept 2017
802.11ba for Main Stream Devices
First of all, for main stream devices, the main radio cannot be turned off completely due to many factors such as
Maintain association status, maintain encryption/authentication status
Maintain internal configuration parameters
Background activities and background interactions with the host for various applications
In order to maintain the various parameters/status on main stream devices, the main radio has to keep certain memory, clocks and processing on, which consumes power, and we call it retention power
The more sophisticated the device is, the more memory is needed, and the higher the retention power is consumed
For main stream devices, the retention power can be higher than ba radio, and such power cannot be eliminated even if ba is used
As a consequence, the power saving benefits for mainstream devices mainly come from Beacon reception elimination
Apple

6. 802.11ba for Main Stream Devices (cont.)
Sept 2017
802.11ba for Main Stream Devices (cont.)
Secondly, mainstream devices have much higher battery capacity than IoT devices, and thus the percentage of power saving brought by ba for mainstream devices would be much smaller than for IoT devices
For example, using the power parameters in ax simulation scenario document [2], assume 3m Beacon reception time, 900ms Beacon reception interval, 3000mAh battery [3], 3.6V, assume WUR consumes 110uW, assume Wi-Fi spent 10 hours Idle in a day, then the power saving benefit is
Legacy operation: average power = (3/900*Rx power+897/900*Sleep power)=0.45uW
Total battery saving=(0.45mW-0.1mW)*10hours/(3000mAh*3.6V)=0.03%
In legacy mode, the average/max latency is 450/900ms. This latency may be too long for some IoT applications, but is considered acceptable for most applications on mainstream devices
Note that a different implementation architecture may result in different power saving percentage. However, due to the large battery and the loose latency requirements on mainstream devices, we do not expect very significant power saving benefit for mainstream devices
Note that the gain for IoT devices can be quite significant due to much smaller battery capacity and more stringent latency requirement
Apple

7. 802.11ba for Main Stream Devices (cont.)
Sept 2017
802.11ba for Main Stream Devices (cont.)
However, as we are defining the new standard targeting at power saving, we would like to see that this technology can bring more power saving benefits for mainstream devices without introducing complex mechanism
In fact, current ba design is (almost) ready to save more power
Apple

8. What Other Power Can be Saved by 802.11ba?
Sept 2017
What Other Power Can be Saved by ba?
To save more power, we have to look for power reduction from activities other than Beacon reception. An example is below.
[1] pointed out the AP re-discovery issue in Usage Model 3, i.e., STA moves out of the range of current AP, and thus needs to discover other APs
Currently, discovering nearby APs on main radio requires the STA to do passive or active scan which consumes quite some power
In fact, there are many background scans on mainstream devices, which consumes much higher power than the Beacon reception power itself
Since WUR is an ultra-low power receiver, offloading some of the passive background scans to WUR can significantly save even more power
In other words, enabling WUR to scan for unassociated APs not only saves power on passive scanning, but also addresses the AP re-discovery problem introduced by WUR itself
Apple

9. Usage Model x: Smart Scanning
Sept 2017
Usage Model x: Smart Scanning
Use case 1: Ultra-low power location scan
Mobile devices sometimes scan through multiple channels for nearby APs, and use the measured Wi-Fi signal strength for improved location services. Scanning on main radio consumes higher power than WUR radio. In addition, scanning on main radio has the risk of conflicting with regular data exchange.
In WUR-facilitated location scan, the mobile device scans through the channels using the WUR receiver, and uses the signal strength measured from WUR packets received from adjacent APs to provide additional information to the location services on the mobile device. In other words, some of the location scan on main radio can be offloaded to WUR radio.
Because WUR consumes much less power than main radio, WUR facilitated location scan provides an ultra-low power location scan mechanism.
Use case 2: Ultra low power roam scan
Mobile devices sometime scan for roaming purposes. These roam scan sometimes is triggered when link quality degrades. These roam scan takes time because the scan is typically done on multiple channels, and on each channel the device either conducts active scan during which it sends a probe request and typically stays awake until it receives a probe response, or passive scan during which it dwells on each channel for at least a Beacon interval to receive a Beacon. As a consequence, scanning through multiple channels introduces roaming latency and consumes power. Sometimes, it runs into conflict with regular data exchange.
In WUR-facilitated roam scan, the mobile device passively scans through multiple channels using WUR, and collects basic information about nearby APs. The collected info can be used to facilitate the devices’ roaming decisions.
Because WUR consumes much less power than main radio, WUR-facilitated roam scan provides an ultra-low power roam scan. In addition, due to the low power operation, WUR scan can be performed quite frequently in the background, and thus roaming information can be readily available whenever needed, i.e., it reduces roaming latency.

10. Two Basic Requirements
Sept 2017
Two Basic Requirements
802.11ba should define frame format (or one type of frame format) that allows unassociated STAs to interpret the AP’s identity
The transmission frequency of such frames do not need to be frequent, 10s of seconds should be enough, since Wi-Fi devices have low mobility
For frames that can be decoded by unassociated STAs, the AP’s identifier should have very low collision probability
When these two basic requirements are met, WUR is ready to be used to solve the AP re-discovery problem while saving more power on main radio passive scan
Apple

11. Sept 2017
Strawpoll
Do you agree to include page 8 into ba usage model document?
Yes No
Abs
Apple

12. Sept 2017
Strawpoll
Do you agree to define a type of WUR frame that can be decoded by unassociated STAs?
Yes No
Abs
Apple

13. Reference [1] 11-17-0029-07-00ba-wur-usage-model-document
Sept 2017
Reference
[1] ba-wur-usage-model-document
[2] ax-simulation-scenarios
[3] with-3-000mah-batteries-or-larger-made-to-last-longer
Apple